Liquid Crystal Display (LCD) devices are used to display images, including symbols, such as text characters and/or pictures. LCD devices have a display screen with a number of image elements (or pixel elements) that are refreshed at a refresh rate generally above 25 Hz, with values being about 60 Hz in many instances. The display images on the LCD devices may be monochromatic or color.
LCD devices can include a backlight element that provides light through an array of liquid crystal elements that form each pixel of the LCD device. The liquid crystal elements provide the color and transmittance of light (i.e., the luminance) at the location of the pixel.
A succession of image frames can be used to display an image on the LCD device. The light of the successive frames displayed on the LCD device is integrated by the human eye. If the number of displayed image frames per second (i.e., the refresh rate) is sufficiently high, images being displayed in a continuous way can create the illusion of motion. One issue with the use of some LCD devices, however, is that of luminance flashes or luminance jumps as the displayed image frame changes. These flashes and/or jumps are also referred to as flicker.
Flashes and/or jumps on LCDs can be due to differences between the rise and fall rates of pixel luminance changes (i.e., the turn ON and turn OFF times of the LCD pixel elements), for example, when large numbers of pixels are simultaneously being changed. For example, flashes on an LCD can occur when a high contrast image is shifted (or scrolled) one pixel up, down, left, and/or right on the screen. The rise and fall rates of LCD pixel luminance changes can also be affected by the initial and final color state (i.e., image content), LCD type, manufacturing process variation, temperature variation, and viewing angle. Human eye sensitivity to the luminance jumps on LCDs may also vary with each individual.
A scrolling image, such as a sonar waterfall, is an example where flashes and/or jumps can occur with each scroll step of the image. When the image is scrolled, a large number of adjacent pixel elements may be changing from light to dark at the same time that a large number of adjacent pixel elements are changing from dark to light. Differing rise and fall rates (i.e., ON/OFF times of the adjacent pixel elements) during these complementary pixel transitions may result in flashes and/or jumps in the LCD display.